Evaluation of the production of second generation Ethanol by co-culture of saccharomyces cerevisiae and pachysolen tannophilus immobilized in Sodium alginate

Abstract

The production of an alternative form of fuel that replaces fossil fuels has been increasingly studied due to the environmental impacts generated by its excessive use, as well as the depletion of these fossil energy sources. Ethanol obtained from the crushing of sugar cane has been used as a substitute for these fuels, mainly in the automotive area. However, alternative sources are being studied to produce the so called second generation bioethanol. This would avoid competition for food producing agricultural areas and agroindustrial waste is a great source for obtaining it. In general, these residues are not always completely reused and are disposed of inappropriately in the environment, becoming contaminants. Therefore, the use of agroindustrial waste can become a renewable source of energy, in addition to reducing environmental impacts. The objective of this work is to produce second generation bioethanol as an alternative to the one currently used, using the rice husk hydrolyzate by the consortium formed by Saccharomyces cerevisiae and Pachysolen tannophilus. For this, an acid hydrolysis was performed with 2% sulfuric acid during 10 minutes of heating in an autoclave, after which the hydrolyzate was detoxified with the use of activated carbon. The crude and detoxified hydrolysates were used as a substrate for the fermentation medium with an initial concentration of 50 mg/mL of reducing sugars. The fermentation process with the use of both yeasts in the crude hydrolyzate medium, in the detoxified medium and in a synthetic medium composed of glucose, was carried out for 24 h, 30º C, 0 rpm and pH 6.5. The best results for the ethanol production of Saccharomyces cerevisiae was the synthetic medium with 20.6 mg/mL. For the yeast Pachysolen tannophilus, its highest production was in a synthetic medium with 11.67 mg/mL. The intercropping of the two yeasts proved to be efficient with a greater ethanol production reaching 21.5 mg/mL, the hydrolyzed and detoxified media showed great potential for ethanol production both in intercropping and in monoculture.